1. Field of the Invention
The present invention relates to a catheter (1) comprising an outer tube (2); an inner tube (3); and a balloon (4) fixed at its proximal sleeve (5) to the outer tube (2) and at its distal sleeve (6) to the inner tube (3). More specifically, the present invention relates to a catheter with an inner tube (3) comprising an elastic segment (7).
2. Background Information
Non-invasive procedures such as percutaneous transluminal angioplasty (PTA), percutaneous transluminal coronary angioplasty (PTCA), stent delivery and deployment, predilatation before stent placement, postdilatation after stent placement, radiation treatment, delivery of a drug at a lesion site and other procedures are used in the treatment of intravascular disease. These therapies are well known in the art and usually utilize a balloon catheter pushed over a guide wire. After a guiding catheter is placed into the patient's main vessel, a guide wire is advanced in the guide catheter and beyond the distal end of the guide catheter. The balloon catheter is then advanced over the guide wire until it reaches the treatment site at the lesion or stenosis. The balloon is inflated to compress the lesion site and dilate the previous narrowed lesion or stenosis site. If the balloon carried a stent and/or drug, the stent and/or drug is delivered at the site when the balloon is inflated. Likewise, further therapies may also use a balloon catheter for the treatment of the lesion site. Balloon catheters are well known in the art. U.S. Pat. No. 5,047,045 and U.S. Pat. No. 5,156,594 for example describe general concepts of angioplasty catheters.
In PTCA applications, the balloon is usually inflated to pressures higher than the nominal pressure but less than rated burst pressure in order to achieve a slight overdilatation. When the catheter is inflated to pressures higher than the nominal pressure the balloon starts to grow in diameter, but also in length. As the inner tube usually does not grow to the same extend as does the balloon, the inflated balloon tends to bend in one direction. This behaviour is also known as “banana shape effect”. On the other hand, once the balloon is inflated and grows, the inner tube being attached to the distal sleeve of the balloon is also forced to stretch itself in the longitudinal direction. This longitudinal growth of the inner tube results in an irreversible and visible over-expansion of the material and results in an “S-shaped” inner tube after deflation of the balloon of the catheter.